Legume Genomics and Genetics 2024, Vol.15, No.3, 126-139 http://cropscipublisher.com/index.php/lgg 130 3.6 CRISPR/Cas9 and other gene editing technologies CRISPR/Cas9 and other gene editing technologies have revolutionized plant breeding by enabling precise modifications to the genome. In soybean breeding, CRISPR/Cas9 has been used to introduce targeted mutations and edit genes associated with important traits such as yield, disease resistance, and stress tolerance. For instance, a study demonstrated the successful use of CRISPR/Cas9 to generate soybean lines with targeted insertions and deletions, achieving mutation rates of up to 90% at the target site. This technology allows for the rapid development of new soybean varieties with enhanced traits without the need for traditional breeding cycles. The ability to precisely edit specific genes makes CRISPR/Cas9 a powerful tool for soybean breeding, enabling the development of varieties that can meet the demands of changing environmental conditions and market needs. 4 Applications of Genomic Tools in Soybean Breeding 4.1 Enhancing yield and quality Genomic tools have revolutionized soybean breeding by enabling more precise and efficient enhancement of yield and quality traits. Techniques like genomic selection (GS), genome-wide association studies (GWAS), and marker-assisted selection (MAS) have significantly improved the selection process for high-yielding and high-quality soybean varieties. For instance, GS has shown high predictive accuracies for yield and seed protein content, making it a valuable tool for soybean breeders. Studies have demonstrated that GS can explain up to 39% of the phenotypic variation in yield and 32% in seed protein content, providing a robust framework for selecting superior genotypes (Figure 2) (Duhnen et al., 2017). Furthermore, the use of CRISPR/Cas9 has opened new avenues for improving soybean traits by allowing precise gene editing to enhance yield and quality traits. This technology has been used to develop soybean mutants with better yield and quality, demonstrating its potential to revolutionize soybean breeding. 4.2 Improving resistance to pests and diseases Improving resistance to pests and diseases is a critical application of genomic tools in soybean breeding. Genomic approaches like GWAS, QTL mapping, and genome editing have been employed to identify and utilize resistance genes. For instance, the integration of genetic analysis, molecular biology, and genomic approaches has drastically enhanced our understanding of genetic control of nematode resistance. This has led to the identification of major resistance loci, such as Rhg1 and Rhg4, which are crucial for breeding nematode-resistant soybean varieties (Kim et al., 2016). Additionally, genome editing tools like CRISPR/Cas9 have been employed to develop soybean varieties with enhanced resistance to pathogens by targeting specific genes involved in disease susceptibility and resistance (Yin and Qiu, 2019). 4.3 Abiotic stress tolerance (drought, heat, salinity) Abiotic stress tolerance is a critical focus in soybean breeding due to the adverse effects of environmental stresses such as drought, heat, and salinity on crop yield. Genomic tools have greatly enhanced our ability to identify and incorporate genes associated with stress tolerance into soybean breeding programs. For instance, quantitative trait loci (QTL) mapping and genome-wide association studies (GWAS) have identified key genomic regions linked to drought tolerance, enabling the development of soybean varieties that can thrive under water-limited conditions. Studies have identified several transcription factors (TFs) like DREBs, ERFs, ZIP, WRKY, and MYB that play significant roles in conferring tolerance to drought, heat, and salinity. The HD-Zip gene family, for example, has been found to impart tolerance to both drought and saline environments in soybeans. CRISPR/Cas9 genome editing has been utilized to create mutations in genes such as GmAITR, resulting in enhanced salinity tolerance. Mutant soybean lines showed improved performance under saline conditions without detrimental fitness costs (Wang et al., 2021). Advances in genomic technologies and high-throughput phenotyping have facilitated the identification of drought-tolerant traits such as root system architecture and canopy wilting, contributing to the breeding of resilient soybean varieties (Valliyodan et al., 2016).
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